The present invention relates to a multiplexing method for multimedia communication, and more particularly, to a multiplexing method which is compatible with H.223 protocol by changing a header of a multiplex-protocol data unit (MUX-PDU).
In general, H.324 recommendation prescribes a multiplexing of video and audio signals which is effective in an error-prone channel such as a wireless channel, and includes H.223 multiplexing, H.245 controlling, H.263 video CODEC and G.723.1 audio CODEC. Also, H.223 multiplexing is recommended as a method for multiplexing video, audio and other data in protocol data units (PDU) in order to realize a video telephone and video conferencing in a total digital is telecommunication network by the ITU-T (the telecommunication standardization sector of the International Telecommunication Union). Also, the H.324 recommendation includes Mode 1 having high complexity and Mode 3 without having complexity. According to Mode 1, while generating a variable length packet an unequal error protection (UEP) is performed by adopting a rate compatible punctured convolutional (RCPC) encoder/decoder (CODEC) in an adaptation layer which is an upper layer. Also, an automatic request for retransmission (ARQ) is used to maintain overall quality of service (QOS) even though the channel throughput decreases. However, the Mode 1 has a high complexity at a portion of RCPC CODEC, which increases the complexity of the overall system. Thus, it is difficult to implement a real-time process. Also, the total channel throughput of the system may decrease rapidly since it adopts a retransmission method. For example, the channel throughput is 50% or less when the retransmission is performed one time, and 33% or less when the retransmission is performed twice. Thus, it is difficult in Mode 1 of H.324 to implement transcoding having compatibility with the conventional H.223. Furthermore, Mode 3 has virtually no error-protection concept, so that error-resiliency in an error-prone channel is very low.
It is an object of the present invention to provide a multiplexing method for multimedia communication, enabling transcoding with H.223 protocol by adding a flag which is similar to a pseudo noise code (PN CODE) after a high-level data link control (HDLC) flag in the multiplex-protocol data unit (MUX-PDU) by H.223 protocol.
To achieve the object, there is provided a multiplexing method for multimedia communication in H.223 protocol, comprising the steps of: (a) encoding media data; and (b) multiplexing the media data encoded in the step (a) in units of a predetermined frame, and inserting a second flag having a predetermined length with an auto-correlation in the frame after a first flag having the opening and closing of the frame.
Preferably, the second flag of the step (b) has a bit pattern of xe2x80x9c10110010xe2x80x9d.